Modelagem Física de Correntes de Turbidez: Descrição do Processo e Implicações no Estudo dos Depósitos Turbidíticos

The turbidity currents are responsible for the formation of the major hydrocarbon reservoirs around the world; however the fundamentals of such currents, both in theory and practice, are still unexplored to exhaustion nowadays. The description of initialization, transportation and deposition mechanisms of this process is surrounded by uncertainty. These uncertainties had inspired the accomplishment of a three series of experiments, in order to investigate it using two different physicals models. It were analyzed the geometrical, dynamical and depositional features of a turbidity current attempting to match the results of physical modeling to those found in natural outcrop. Granular materials are tested and grain size ranges for simulation are evaluated. Density currents with different densities, grain sizes, fluid injection rate and volume were generated. Therefore density current evolution, current velocity, geometric features, and bed forms were registered. The results show that velocity increases for larger current densities or smaller grain sizes and that the height of the current head increases when the current density decreases. The deposition volumes present a general tendency of exponential decline; the grain size range of the deposits decreases towards the distal portion of the channel. The results also show that advancing velocity and bed forms (it was observed the successive development of planar upper flow regime surfaces, low sinuous-ripples, middle sinuous-ripples, meandering channels and linear channels) depend basically of the flow oscillations identified in the fluid injection rate. The simulations presented intended to collaborate with the understanding of the natural phenomena, relating the current behaviour (flow parameters) with the generated deposit (turbidites), as well as indicated the applicability of physical modelling on the field of deep-water sedimentation and its reliability as a tool for hydrocarbon reservoir prediction.The turbidity currents are responsible for the formation of the major hydrocarbon reservoirs around the world; however the fundamentals of such currents, both in theory and practice, are still unexplored to exhaustion nowadays. The description of initialization, transportation and deposition mechanisms of this process is surrounded by uncertainty. These uncertainties had inspired the accomplishment of a three series of experiments, in order to investigate it using two different physicals models. It were analyzed the geometrical, dynamical and depositional features of a turbidity current attempting to match the results of physical modeling to those found in natural outcrop. Granular materials are tested and grain size ranges for simulation are evaluated. Density currents with different densities, grain sizes, fluid injection rate and volume were generated. Therefore density current evolution, current velocity, geometric features, and bed forms were registered. The results show that velocity increases for larger current densities or smaller grain sizes and that the height of the current head increases when the current density decreases. The deposition volumes present a general tendency of exponential decline; the grain size range of the deposits decreases towards the distal portion of the channel. The results also show that advancing velocity and bed forms (it was observed the successive development of planar upper flow regime surfaces, low sinuous-ripples, middle sinuous-ripples, meandering channels and linear channels) depend basically of the flow oscillations identified in the fluid injection rate. The simulations presented intended to collaborate with the understanding of the natural phenomena, relating the current behaviour (flow parameters) with the generated deposit (turbidites), as well as indicated the applicability of physical modelling on the field of deep-water sedimentation and its reliability as a tool for hydrocarbon reservoir prediction

Modelling hydrodynamic interactions between deformable droplets

Deposited with permission of the author. © 2007 Rogerio Manica.Understanding deformations during interaction of colloidal or nano droplets. has important implications in a wide range of applications such as flotation collection and emulsion stability. The present work is important and necessary because current models are unable to properly describe recent experimental results obtained using the Atomic Force Microscope (AFM) and Surface Force Apparatus (SFA). We revisit and improve on theories involving interacting deformable droplets. A detailed theoretical model of the experiments, which accounts for surface forces, hydrodynamic interactions, droplet deformation and AFM cantilever detection, has been developed. The new feature of the model is the use of matched asymptotic expansions to derive a new boundary condition at constant volume to obtain results that are independent of the size of the computational domain. The AFM experiments provide measurements of dynamical forces between two interacting droplets as well as between a drop and a colloidal particle of micrometre radii in solution when they are driven together and then are retracted from each other. The SFA experiments measure (time dependent) surface profiles of a millimetre size mercury drop interacting with a mica surface. Different configurations have been studied including mechanical and electrical perturbations to a thin film stabilized by double layer repulsion. Interesting experimental features were observed when approaching or retracting the mica from the mercury drop

Effect of plant spacing on the yield of the yellow passion fruit at Viamão, RS, Brazil

Este trabalho foi realizado em Viamão, RS, e teve como objetivo verificar o efeito de seis espaçamentos de plantio sobre o peso e o número de frutos produzidos por planta e por hectare, assim como sobre o peso médio dos frutos de maracujá-amarelo (Passiflora eduhs f.flavicarpa Deg.). Nas linhas de plantio foram utilizados os espaçamentos de 200, 2,75, 3,50, 4,25, 5,00, e 5,75 m, enquanto nas entrelinhas foi mantida a distância de 2,50 m, correspondendo às densidades de 695 a 2.000 plantas/ ha. As colheitas ocorreram de janeiro a setembro de 1981 e 1982, com dois picos distintos de produção. A análise das duas safras evidenciou resposta quadrática para o peso de frutos por planta, e linear para o número de frutos, com a resposta máxima tendendo para o espaçamento de 2,50 x 5,00 m. A produção por hectare (peso e número de frutos) apresentou uma relação linear decrescente com o aumento das distâncias de plantio, sendo que o espaçamento de 2,50 x 2,00 m correspondeu ao rendimento máximo. Sugeriu-se que os espaçamentos de 2,50 x 3,50 me 2,50 x 4,25 m são os mais adequados para a cultura, representando o ponto de equilíbrio entre as produções por planta e por hectare. O peso médio dos frutos não foi influenciado pelos espaçamentos de plantio em ambas as safras colhidas.The experiment was stablished at Viamão, AS, Brazil, with the objective of determining the effect of six planting distances on the number and weight of fruit per plant and por hectare and also on the average weight of the fruit of the yellow passion fruit (Passiflora edu/is f. flavicarpa Degj. The spaces in the rows were 2,00. 2,75, 3,50, 4,25, 5,00 and 5,75 m and 2,50 m between rows, corresponding to densities ranging from 695 to 2000 plants/ha. The harvesting season began in January and extended until September during 1981 and 1982, with two distinct pealçs of production. For the two harvests, the effect of spacing on frult weight per plant was quadratic and on fruit number was linear, with the tendency of having the maximum responses at 2,50: x 5,00 m spacing. The waight and number of fruits per hectare decreasod Iinearly with the spacing in the row, having the rnaximum value at 2,50 x 2,00 m spacing. The spacings of 2,50 ,c 3,50 ru and 2,50 x 4,25 m are suggested as the most adequate for this crop because they represent the balancing point between production per plant and por hectare. The spacing did not affect the average weight af the fruit ri both harvests

Drainage of the air-water-quartz film: experiments and theory

Experimental results of the kinetics of drainage of the trapped water film between an approaching air bubble and a quartz plate have been analysed using recent theoretical advances in formulating and solving the flow problem in deformable films. Excellent agreement is obtained between experimental data and a model that assumes the bubble-water interface is tangentially immobile in its hydrodynamic response. The coupling between hydrodynamic pressure, disjoining pressure and film deformation is critical in determining the dynamic behaviour of the drainage process. The Reynolds parallel film model that omits the effects of film deformation predicts results that are qualitatively incorrect

Effect of plant spacing on the yield of the yellow passion fruit at Viamão, RS, Brazil

Este trabalho foi realizado em Viamão, RS, e teve como objetivo verificar o efeito de seis espaçamentos de plantio sobre o peso e o número de frutos produzidos por planta e por hectare, assim como sobre o peso médio dos frutos de maracujá-amarelo (Passiflora eduhs f.flavicarpa Deg.). Nas linhas de plantio foram utilizados os espaçamentos de 200, 2,75, 3,50, 4,25, 5,00, e 5,75 m, enquanto nas entrelinhas foi mantida a distância de 2,50 m, correspondendo às densidades de 695 a 2.000 plantas/ ha. As colheitas ocorreram de janeiro a setembro de 1981 e 1982, com dois picos distintos de produção. A análise das duas safras evidenciou resposta quadrática para o peso de frutos por planta, e linear para o número de frutos, com a resposta máxima tendendo para o espaçamento de 2,50 x 5,00 m. A produção por hectare (peso e número de frutos) apresentou uma relação linear decrescente com o aumento das distâncias de plantio, sendo que o espaçamento de 2,50 x 2,00 m correspondeu ao rendimento máximo. Sugeriu-se que os espaçamentos de 2,50 x 3,50 me 2,50 x 4,25 m são os mais adequados para a cultura, representando o ponto de equilíbrio entre as produções por planta e por hectare. O peso médio dos frutos não foi influenciado pelos espaçamentos de plantio em ambas as safras colhidas.The experiment was stablished at Viamão, AS, Brazil, with the objective of determining the effect of six planting distances on the number and weight of fruit per plant and por hectare and also on the average weight of the fruit of the yellow passion fruit (Passiflora edu/is f. flavicarpa Degj. The spaces in the rows were 2,00. 2,75, 3,50, 4,25, 5,00 and 5,75 m and 2,50 m between rows, corresponding to densities ranging from 695 to 2000 plants/ha. The harvesting season began in January and extended until September during 1981 and 1982, with two distinct pealçs of production. For the two harvests, the effect of spacing on frult weight per plant was quadratic and on fruit number was linear, with the tendency of having the maximum responses at 2,50: x 5,00 m spacing. The waight and number of fruits per hectare decreasod Iinearly with the spacing in the row, having the rnaximum value at 2,50 x 2,00 m spacing. The spacings of 2,50 ,c 3,50 ru and 2,50 x 4,25 m are suggested as the most adequate for this crop because they represent the balancing point between production per plant and por hectare. The spacing did not affect the average weight af the fruit ri both harvests

Force balance model for bubble rise, impact, and bounce from solid surfaces

A force balance model for the rise and impact of air bubbles in a liquid against rigid horizontal surfaces that takes into account effects of buoyancy and hydrodynamic drag forces, bubble deformation, inertia of the fluid via an added mass force, and a film force between the bubble and the rigid surface is proposed. Numerical solution of the governing equations for the position and velocity of the center of mass of the bubbles is compared against experimental data taken with ultraclean water. The boundary condition at the air-water interface is taken to be stress free, which is consistent for bubbles in clean water systems. Features that are compared include bubble terminal velocity, bubbles accelerating from rest to terminal speed, and bubbles impacting and bouncing off different solid surfaces for bubbles that have already or are yet to attain terminal speed. Excellent agreement between theory and experiments indicates that the forces included in the model constitute the main physical ingredients to describe the bouncing phenomenon

Dynamic interactions between drops--a critical assessment

Accurate measurements and modelling of time-dependent deformations of colliding liquid drops demonstrate the need to account for drop deformation and film drainage with appropriate initial and boundary conditions and reveal significant quantitative differences with the Stefan-Reynolds flat film model of drop coalescence